Influence of incubation in utero on motility and head-to-head agglutination of ejaculated rabbit spermatozoa.

Ejaculated spermatozoa were rendered immotile by incubation for 8 h at 37 degrees C in 2.9% sodium citrate. Immotile spermatozoa (5 x 10(6)) were surgically inseminated into the uterine lumen of does and samples were recovered from the uterus 5, 15, 30 and 60 min after insemination. Incubation in utero led to a resumption of progressive motility and induced head-to-head agglutination. Motility and head-to-head agglutination were highest (64 and 70% respectively) at 5 min, and declined (48 and 49%) by 60 min. The percentage of spermatozoa with an intact acrosome did not change during the in-utero incubation. When spermatozoa from a single ejaculate were evaluated in different females there was significant variation (P less than 0.01) in the reinitiation of motility and agglutination. Most agglutinated spermatozoa (greater than 96%) had an intact acrosomal membrane while acrosomal integrity of single spermatozoa differed greatly among females. We conclude that the agglutinated (motile with intact acrosomes) and non-agglutinated (usually immotile and with disrupted acrosomes) represent different populations within the uterine lumen.